Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W, *S = open(0).read().split()
H, W, S = int(H), int(W), [list(s) for s in S]

white = sum(s.count(".") for s in S)

Q = deque([(0, 0, 1)])
while Q:
    h, w, count = Q.popleft()
    if (h, w) == (H - 1, W - 1):
        print(white - count)
        quit()

    for nh, nw in [(h, w + 1), (h, w - 1), (h + 1, w), (h - 1, w)]:
        if 0 <= nh < H and 0 <= nw < W and S[nh][nw] == ".":
            S[nh][nw] = "visited"
            Q.append((nh, nw, count + 1))
print(-1)